Various proposals have recently been made on techniques for displaying a stereoscopic image as a result of the progress of optical technologies. One of such techniques is two-glass type three-dimensional viewers such as IMAX THEATER (trademark) capable of presenting stereoscopic display to a user who wears dedicated eyeglasses to see an image formed by an image for the left eye and an image for the right eye in an overlapping relationship. This apparatus enables to present stereoscopic display in the form of a stereogram utilizing parallax between left and right eyes.
Stereoscopic display is also performed with holography utilizing coherent light from a laser or the like. This technique is to display a stereoscopic image by forming a hologram on a dry plate or the like using object light and reference light in advance and by irradiating the hologram with the original reference light to obtain reproduction light.
Techniques for displaying a stereoscopic image without any need for dedicated eyeglasses include the so-called IP (integral photography) method, and the parallax method.
The IP method was proposed by Lippmann. A photographic dry plate is provided on a focal surface of a lens plate called “fly-eye lens” constituted by a multiplicity of small convex lenses; the photographic dry plate is exposed to object light through the lens plate to record a multiplicity of small object images thereon; and the photographic dry plate is thereafter developed, placed in exactly the same position as its initial position and irradiated with light on the back surface thereof.
The parallax method is a method in which strip-shaped images respectively associated with left and right eyes are separately viewed through apertures in the form of vertical grills placed in front of the strip-shaped images.
Among the above techniques, the above-described stereoscopic viewers are inconvenient for a viewer because he or she must wear dedicated eyeglasses and are not suitable for observation for a long time because they present unnatural images which are likely to give fatigue.
The above-described technique for presenting stereoscopic display utilizing holography involves a large scale apparatus at a high manufacturing cost because of the requirement for coherent light from a laser or the like and also results in a reduction of image quality attributable to speckle interference patterns which are characteristic of lasers. Further, holography is suitable for still images but unsuitable for three-dimensional display of dynamic images because it presents stereoscopic display of an object utilizing a hologram formed on a photographic dry plate in advance. This equally applies to the above-described IP method in that it is unsuitable for dynamic images because it involves a step of recording a multiplicity of small object images on a photographic dry plate in advance.
The parallax method that requires no dedicated eyeglasses only presents pseudo-stereoscopic display utilizing parallax between left and right eyes and does not allow three-dimensional display in a true sense. Therefore, although an image can be represented with a stereoscopic sense in the horizontal direction of a screen, it cannot be represented with a stereoscopic sense in the vertical direction and, for example, cannot be viewed by a person who is lying down. Further, since it is a technique utilizing parallax, a change of a view point only results in a view of the same image with a stereographic sense (a sense of depth), and a side of an object will not appear even if the viewer moves the head to look at the object from left and right sides thereof.
Further, in order to implement the parallax method, an object must be photographed in different directions with a plurality of cameras; the films photographed by the cameras must be developed; and the films must be printed on photographic paper through apertures with a plurality of image projectors to form strip-shaped images. Therefore, a large scale apparatus is required to implement the parallax method.
As thus described, according to conventional techniques it is difficult to achieve display of a stereoscopic dynamic image in a true sense with a simple configuration.
Any of the conventional techniques for stereoscopic display only allows a three-dimensional image to be displayed in a predetermined position. Therefore, the conventional techniques for stereoscopic display have low rendering capability in that it is difficult to achieve a representation in which a three-dimensional image is moved toward or away from the viewer, for example.